Science is far from a perfect instrument of knowledge. It is just the
best we have. In this respect, as in many others, it's like democracy.
[...]

The scientific way of thinking is at once imaginative and disciplined.
This is central to its success. Science invites us to let the facts
in, even when they don't conform to our preconceptions. It counsels
us to carry alternative hypotheses in our heads and see which best
fits the facts. [...] This kind of thinking is also an essential tool
for a democracy in an age of change.

One of the reasons for its success is that science has built-in,
error-correcting machinery at its very heart. [...]

Every time a scientific paper presents a bit of data, it's accompanied
by an error-bar--a quiet but insistent reminder that no knowledge is
complete or perfect. It's a calibration of how much we trust what we
think we know. If the error bars are small, the accuracy of our
empirical knowledge is high; if the error bars are large, then so is
the uncertainty in our knowledge. Except in pure mathematics, nothing
is known for certain (although much is certainly false). [...]

Humans may crave absolute certainty; they may aspire to it; they
may pretend, as partisans of certain religions do, to have attained
it. But the history of science--by far the most successful claim to
knowledge accessible to humans--teaches that the most we can hope
for is successive improvement in our understanding, learning from
our mistakes, an asymptotic approach to the Universe, but with the
proviso that absolute certainty will always elude us. [...]

Science may be hard to understand. It may challenge cherished
beliefs. When its products are placed at the disposal of politicians
or industrialists, it may lead to weapons of mass destruction
and grave threats to the environment. But one thing you have to
say about it: It delivers the goods.

Not every branch of science can foretell the future--paleontology
can't--but many can and with stunning accuracy. If you want to
know when the next eclipse of the Sun will be, you might try
magicians or mystics, but you'll do much better with scientists.
They will tell you where on Earth to stand, when you have to be
there, and whether it will be a partial eclipse, a total eclipse,
or an annular eclipse. They can routinely predict the solar
eclipse, to the minute, a millennium in advance. You can go to
the witch doctor to lift the spell that causes your pernicious
anemia, or you can take vitamin B12.
If you want to save your child from polio, you can pray or you
can inoculate. If you're interested in the sex of your unborn
child, you can consult plumb-bob danglers all you want (left-right,
a boy; forward-back, a girl--or maybe it's the other way around),
but they'll be right, on average, only one time in two. If you
want real accuracy (here, 99 percent accuracy), try amniocentesis
and sonograms. Try science.

Think of how many religions attempt to validate themselves with
prophecy. Think of how many people rely on these prophecies,
however vague, however unfulfilled, to support or prop up their
beliefs. Yet has there ever been a religion with the prophetic
accuracy and reliability of science? There isn't a religion on
the planet that doesn't long for a comparable ability--precise,
and repeatedly demonstrated before committed skeptics-- to
foretell future events. No other human institution comes close.

Is this worshiping at the altar of science? Is this replacing
one faith by another, equally arbitrary? In my view, not at all.
The directly observed success of science is the reason I
advocate its use. If something else worked better, I would
advocate the something else. Does science insulate itself from
philosophical criticism? Does it define itself as having a
monopoly on the "truth"? Think again of that eclipse a thousand
years in the future. Compare as many doctrines as you can think
of, note what predictions they make of the future, which ones
are vague, which ones are precise, and which doctrines--every
one of them subject to human fallibility--have error-correcting
mechanisms built in. Take account of the fact that not one of
them is perfect. Then simply pick the one that in a fair
comparison works (as opposed to feels) best. If different doctrines
are superior in quite separate and independent fields, we are
of course free to choose several--but not if they contradict
one another. Far from being idolatry, this is the means by which
we can distinguish the false idols from the real thing.

Again, the reason science works so well is partly that built-in
error-correcting machinery. There are no forbidden questions
in science, no matters too sensitive or delicate to be probed,
no sacred truths. [...]

You sit in at contentious scientific meeting. You find university
colloquia in which the speaker has hardly gotten 30 seconds into
the talk before there are devastating questions and comments from
the audience. You examine the conventions in which a written
report is submitted to a scientific journal, for possible
publication, then is conveyed by the editor to anonymous referees
whose job is to ask: Did the author do anything stupid?
Is there anything here that is sufficiently interesting to be
published? What are the deficiencies of this paper? Have the
main results been found by anybody else? Is the argument
adequate, or should the paper be resubmitted after the author
has actually demonstrated what is here only speculated on?
And it's anonymous: The author doesn't know who the critics are.
This is the everyday expectation in the scientific community.
[View a sample review form.]

Why do we put up with it? Do we like to be criticized?
No, no scientist enjoys it. Every scientist feels a proprietary
affection for his or her ideas and findings. Even so, you don't
reply to critics, Wait a minute; this is really a good idea;
I'm very fond of it; it's done you no harm; please leave it
alone. Instead, the hard but just rule is that if the ideas
don't work, you must throw them away. Don't waste neurons on
what doesn't work. Devote those neurons to new ideas that
better explain the data. The British physicist Michael Faraday
warned of the powerful temptation

to seek for such evidence and appearances as are in the
favour of our desires, and to disregard those which
oppose them... We receive as friendly that which agrees
with [us], we resist with dislike that which opposes us;
whereas the very reverse is required by every dictate of
common sense.

Valid criticism does you a favor.

[...] Scientists do not seek to impose their needs and wants
to Nature, but instead humbly interrogate Nature and take
seriously what they find. We are aware that revered scientists
have been wrong. We understand human imperfection. We insist
on independent and--to the extent possible--quantitative
verification of proposed tenets of belief. We are constantly
prodding, challenging, seeking contradictions or small,
persistent residual errors, proposing alternative explanations,
encouraging heresy. We give our highest rewards to those who
convincingly disprove established beliefs. [...]

This is one of the reasons that the organized religions do
not inspire me with confidence. Which leaders of the major
faiths acknowledge that their beliefs might be incomplete or
erroneous and establish institutes to uncover possible
doctrinal deficiencies? Beyond the test of everyday living,
who is systematically testing the circumstances in which
traditional religious teachings may no longer apply?

But of course I might be wrong.

[...] The values of science and the values of democracy are
concordant, in many cases indistinguishable. Science and
democracy began--in their civilized incarnations--in the
same time and place, Greece in the seventh and sixth
centuries B.C.